Traditional safety razor blades have a substantial width perpendicular to the cutting edge and are held in position in the razor by clamping between members which engage opposite surfaces of the blade itself. It has been proposed to replace such blades by very narrow blade strips, which as well as being economical of material, are easily rinsed clean after use and can be so mounted as to have a desirably greater degree of flexibility than conventional blades. To give the narrow blade strips adequate rigidity, it has been proposed to hold them under longitudinal tension and/or to impart a special cross-sectional shape to the blade strip.
It has also been proposed to provide a shaving unit comprising a narrow elongated blade strip sharpened along one longitudinal edge and an elongated support member which is of greater length than the blade strip, and which is formed over a length at least equal to the active shaving length of the blade strip with a substantially flat surface, one face of the blade strip being secured along its length to the surface of the support member with the cutting edge of the blade projecting clear of the support member. Shaving units of this type are disclosed in U.S. Pat. Nos. 4,063,357 and 4,084,316. In the production of such shaving units, the blade strips are positioned with respect to the support member and secured by the use of conventional welding techniques.
Existing welding techniques include gas welding which employs a burning gas such as acetylene or hydrogen, are welding in which the fusion energy is obtained from an electric arc, resistance welding in which current is passed through the workpiece placed between the ends of two electrodes, ultrasonic welding where the parts to be welded are clamped between anvils through which high frequency mechanical vibration is coupled to the workpiece to effect solid state bonding of the adjoining surfaces, electron beam welding in which a focused beam of electrons supplies the fusion energy to the workpiece which is held in a vacuum environment, and laser welding in which the fusion energy is supplied by a focused beam of infra-red radiation. An optimum welding technique would include the desirable features from all methods; that is, precise control of position and size of weld area, precise control of energy input, high welding speed capability, minimum heat affected zone, minimum disruption of metallurgical structure, a clean process free of oxidation reactions, a non-contact operation, and easy application in an automatic manufacturing process. Of the welding processes listed, laser welding combines a unique combination of advantages that make it of distinct interest in specialized welding applications. These advantages include: (1) The laser beam can be optically focused to provide precise position and size control of the weld area; (2) power density of the focused spot can be adjusted and precisely controlled from low to very high values; (3) very high weld speeds are possible by means of high power densities and/or pulsed laser operation; (4) with high welding speeds the resulting heat affected zone is very small and disruption of the metallurgical structure at a distance from the fusion zone is minimized; (5) the process is very clean and oxidation reactions can be prevented easily by use of an inert cover gas; (6) welding is performed in the open unlike electron beam welding whereby the operation is typically performed in a vacuum; (7) the process is of the non-contact type; and (8) laser welding can be readily integrated into a high speed automatic assembly process.